War Caster feat is only thing any caster need, to be able easily maintain concentration.
I agree that War Caster and Resilient: CON are great feats to help maintain concentration. However, I don't think it will feel good to be punished harder in BG3 than in 5e, because you haven't picked up a feat yet.
Also keep in mind that depending on where the level cutoff is, most spellcasters only get 2-3 ASI's, and still need to improve their spellcasting modifier.
